The current invention relates to Telecommunication Networks of a kind which comprises an Intelligent Network and the management of call congestion therein.
Operators of telecommunication networks are continually seeking to provide enhanced functionality for users. Introduction of Intelligent Networks (IN) has significantly improved the flexibility and range of features available to the user.
Intelligent Network is a term for a public network architecture which has been adopted internationally. By changing the relationship of the basic call (i.e. a person to person telephone call) to added value services (e.g. call waiting, three party call, etc.) it has been possible to separate off the features and provide them separately within the network and to provide a defined interface between the basic call and the added value services. Within the IN architecture, the services are provided in a separate physical entity within the network known as a service control point or SCP which influences the progress of a call which is contained within the service switching point or SSP.
The SSP comprises a service switching function (SSF) and a call control function (CCF). In conventional networks, incoming calls to the IN arrive at the CCF. If the CCF can handle the IN call it passes an initiating message to the SSF.
Most IN implementations within a telecommunications network are as overlayed networks which are connected to the traffic sources by signalling system number 7 (SS7) interfaces.
A known problem in IN occurs when the rise in traffic volume for a particular IN service temporarily reduces the capacity for other IN services. For example, if an unscheduled mass-call event occurs to a particular IN service the result can be that incoming routes are swamped rendering them unavailable to support other traffic. A known solution to this problem is Call-Gapping. The known Call-Gap operation according to the current standards involves operation by the CCF in receiving the incoming call and passing it to the associated SSF which then processes the call further. If Call-Gapping is enabled either a proportion of all incoming calls, or a proportion of all calls from a particular source are discarded by the IN at the SSF during periods of traffic congestion. The International Telecommunications Union (ITU) has issued telecommunications standards (ITU-T) specifying capability set one (CS.1) and capability set two (CS.2) which both support Call-Gap operation in an IN.